As a bearing device for wheel, there have been developed the following types: a structure called a first generation type in which roller bearings are used in double row combination; a second generation type evolved from the first generation type, in which a vehicle body mounting flange is integrated with an outer member; a third generation type in which one of two inner raceway surfaces of the double row roller bearing is formed on an outer periphery of a hub wheel provided with a wheel mounting flange; and a fourth generation type in which the one of the two inner raceway surfaces of the double row roller bearing is formed on the outer periphery of the hub wheel, and another of the two inner raceway surfaces of the double row roller bearing is formed on an outer periphery of an outer joint member of a constant velocity universal joint.
For example, Patent Literature 1 below describes one example of the bearing device for wheel of the above-mentioned third generation type. The bearing device for wheel described in Patent Literature 1 comprises: a bearing for wheel comprising a hub wheel provided with a flange to be mounted to a wheel, and an outer member arranged on an outer peripheral side of the hub wheel; and a constant velocity universal joint comprising an outer joint member to be coupled to the hub wheel. In this bearing device for wheel, the hub wheel and the outer joint member are coupled to each other by press-fitting a male spline provided to a shaft portion of the outer joint member to a female spline provided to a hole portion of the hub wheel, that is, what is called spline fitting. However, coupling of the hub wheel and the outer joint member to each other by spline fitting has problems as follows. First, it is necessary for both the shaft portion of the outer joint member and the hub wheel to be provided with a spline, which leads to a cost increase. Further, regarding fitting of recesses and projections of the male spline and the female spline to each other, which is necessary to perform at the time of press-fitting, when press-fitting is performed by tooth surface fitting, tooth surfaces may be damaged, for example, by being scraped. Meanwhile, when press-fitting is performed by large diameter fitting, backlash in the circumferential direction is liable to occur. The backlash in the circumferential direction may lead to deterioration in torque transmission efficiency and generation of abnormal noise.
In view of the above-mentioned circumstances, the applicants of the present application have proposed a bearing device for wheel described in JP 2009-56869 A (Patent Literature 2), which is capable of solving the above-mentioned various problems. Specifically, projection portions provided to any one of the shaft portion of the outer joint member and the hole portion of the hub wheel and extending in an axial direction are press-fitted to another of the shaft portion of the outer joint member and the hole portion of the hub wheel so that recessed portions are formed with the projection portions along the another of the shaft portion of the outer joint member and the hole portion of the hub wheel. In this way, there is formed a recess-projection fitting structure in which the projection portions and the recessed portions are held in intimate contact at fitting parts with each other, and the hub wheel and the outer joint member are coupled to each other through intermediation of this recess-projection fitting structure.
Further, for example, when the bearing device for wheel is repaired, it may be difficult to repair the bearing device for wheel under a state in which the hub wheel and the outer joint member are coupled to each other. Thus, in order that a bearing part and a joint part can be individually repaired, it is desired that the hub wheel and the outer joint member be separable from each other. Moreover, after the hub wheel and the outer joint member are separated from each other, it is necessary for both the hub wheel and the outer joint member to be re-coupled to each other. In this regard, the above-mentioned recess-projection fitting structure is separable by being applied with a pulling-out force in the axial direction under a state in which the bolt member is removed from the bolt hole provided in the shaft portion. Thus, satisfactory repair operation properties can be secured. Further, after the repair, the above-mentioned recess-projection fitting structure can be re-formed by press-fitting the shaft portion of the outer joint member into the hole portion of the hub wheel. Specifically, the recess-projection fitting structure can be re-formed by screwing the bolt member into the bolt hole provided in the shaft portion. Thus, in order to re-form the recess-projection fitting structure, it is no longer necessary to use a large-scale equipment such as a press machine for press-fitting. Therefore, on site such as an automobile maintenance factory, inspection, repair, and the like of the bearing device for wheel can be easily performed.